Metal cleaning



y 3, 1967 L, v. ABRAMS ETAL 3,320,701

METAL CLEANING Filed Nov. 13, 1963 2 Sheets-Sheet 1 KQQI/ a f 1 INVENTORS Louis V. Ab rams United States Patent 3,320,701 METAL CLEANING Louis V. Abrams and Ralph M. Trent, Hagerstown, Md., assignors to The Pangborn Corporation, Hagerstown, Md., a corporation of Delaware Filed Nov. 13, 1963, Ser. No. 323,381 4 Claims. (Cl. 515) This invention relates to treating metal, and more particularly to cleaning metal surfaces in connection with cold reduction operations.

Heretofore, the surfaces of hot rolled metal workpieces, such as strip, bar or sheet stock, have been cleaned of mill scale and the like prior to reducing, rolling or other cold working operations by specialized acid pickling baths. This pickling bath treatment uses large, expensive acid tanks permanently occupying ordinarily scarce plant floor space, and problems arise with the disposing of quantities of spent acid. Even flash pickling operations which materially reduce exposure time include a number of the same drawbacks, and do not provide satisfactory answers to problems presented in this area.

In addition, previous attempts to clean hot rolled workpieces by blasting the metal surfaces with grit shot and other abrasives have generally proved unsatisfactory since even after mild cold reduction, the workpieces still contained an undesirable amount of surface contamination such as mill scale oxides. It has been found that such contamination may be caused in part by sub-surface contamination being in effect squeezed to the surface in bending, straightening, reducing or other cold work operations. Additionally, surface contaminants may collect upon and build up on cold working rollers to be redeposited on the work.

Accordingly, it is one object of the present invention to provide a new and novel method and apparatus for producing cold reduced metal workpieces having clean surfaces.

Another object of the present invention is to provide a new and novel method and apparatus for removing contaminant from metal workpiece surfaces by a first abrasive blast cleaning before the metal workpieces are cold worked and a secondary cleaning operation after the cold working.

Other objects and advantages of the present invention will become apparent from a study of the following description and drawings wherein:

FIG. 1 is a schematic side view of an assembly for cold rolling and cleaning the surfaces of metal workpieces according to the invention;

FIG. 2 is a schematic side view similar to FIG. 1 showing a modification of the invention;

FIG. 3 is a schematic end view of a known abrasive blasting unit utilized by this invention; and

FIGS. 4A-C are partially sectioned and enlarged views showing metal workpieces at various stages of the process of this invention.

Referring now to the drawings, a metal workpiece is seen and is shown here as fiat strip stock such as hot rolled steel. A driven take up drum 12 simultaneously pulls the steel strip 10 along a generally horizontal path through an assembly of treating units and collects the strip.

In FIG. 1, the metal workpiece is first drawn through an abrasive blast cleaning unit 14 (also see FIG. 3). This unit includes opposed blast wheels 16 fed with abrasive through feed lines 17, 17 for directing abrasive media against both the upper and lower surfaces of the passing workpiece. As is Well-known, such a unit generally includes an elevator 18 for conveying the collected used abrasive media to a feed hopper 20 connected with the feed lines 17, 17. The blast cabinet 22 in which 3,320,701 Patented May 23, 1967 the metal workpiece is blast cleaned further includes closure sealing means 24 at each end to prevent the escape of abrasive media from the cabinet. An air or other separator 25 is also provided between the elevator 18 and the feed hopper for separating contaminant from the abrasive. The unit 14 removes surface contaminant such as mill scale oxides and the like from both upper and lower surfaces of the metal workpiece as it passes therethrough.

The strip stock 10 then is drawn through the nip of a pair of pressure rollers 26 for cold reducing the workpiece as it passes therebetween. Here, an upper roller 28 and a lower roller 30 are provided to create a mechanical upsetting of the surface layers of the metal workpiece to somewhat alter the metal grain structure and provide a workpiece of a desired reduced thickness. In this operation, sub-surface contaminant is exposed.

Finally, the strip stock is drawn through a second blast cleaning unit 32 which is identical with the unit 14. The rotary blast elements 34 of this unit provide a secondary cleaning operation in much the same manner as the rotary blast elements 16 of the unit 14 to remove the exposed sub-surface contaminant.

A somewhat different grade or variety of abrasive may be employed to effect the desired contaminant removal operation on both the upper and lower surfaces of the workpiece.

In FIG. 2 a modification is shown. The final operating unit in this assembly comprises an ultra-sonic cleaning unit 36 instead of the second blasting unit 32 of FIG. 1. The ultra-sonic unit 36 includes a cleaning chamber 38 through which the workpiece is drawn to remove contaminant which is suspended in a cleaning solution containing chemicals. The contaminant settles in the liquid. The contaminant is then preferably filtered from the solution and the solution returned to an equilibrium point. Thereafter, such solution is reusable with only slight additions. The ultra-sonic cleaning unit effects a fin-al cleaning to remove the exposed sub-surface contaminant from the reduced thickness workpiece in much the same manner as the blast cleaning unit 32 discussed above in connection with FIG. 1.

The surface preparation methods of this invention in the FIG. 1 and FIG. 2 embodiments follow generally parallel principles to attain similar beneficial results. Looking at FIGS. 4A-C the workpiece 10 is illustrated in enlarged sectional elevation to show the condition thereof at four separate points along the assembly of operating units. The first point is a section taken at A in FIGS. 1 and 2 showing the condition of the workpiece prior to entering the initial blast cleaning unit 14. The next two points are a section taken at B in FIGS. 1 and 2 and show on the left-hand side of the reducing rollers the condition of the workpiece subsequent to the initial blast cleaning while the condition of the workpiece subsequent to being cold reduced by the roller unit 26 is shown on the right hand side. The final point is a section taken at C in FIGS. 1 and 2 showing the condition of the workpiece subsequent to operation of the final cleaning provided by the units 32 or 36.

In the section at A, the workpiece 10 is characterized by surface contaminant 40 on both the upper and lower surfaces thereof. Additionally, a plurality of surface imperfections 42 in the form of crevices or voids created by the hot rolling forming process contain sub-surface contaminant to a depth from each surface equal in some areas to the range of metal which is to be mechanically upset by the cold reduction process.

The section at B shows on the left-hand side of the rollers that the surface contaminant 40 has been essentially totally removed by the initial blast cleaning operation. Sub-surface contaminant in the zones 42 has not been removed by this initial cleaning step. Such a blast 1 cleaned surface may be rubbed with a clean cloth and will show no indication of contamination.

On the right-hand side of the rollers in the section at B, the thickness of the metal workpiece has been reduced by the roller unit. The voids or crevices 42 have been mechanically Worked out of the surface layers of the metal and essentially erased by the cold working step. The contamination which previously la-y below the workpiece surface in these imperfections has been exposed and in effect squeezed to the surface as at 44 by the reductionroller operation. Any such contaminants which may be driven to the surface and inadvertently collected on the reducing rollers and subsequently redistributed upon the surface of the workpiece will lie totally on the surface of the workpiece in a similar fashion.

In the section at C, thecontaminant driven to the surface of the workpiece by the cold reduction operation has been-essentially totally removed by the final contaminant removal equipment. In the FIG. 1 embodiment, this is accomplished by the blast cleaning unit 32 while in the FIG. 2 embodiment, this is accomplished by the ultrasonic cleaning unit 36. As illustrated diagrammatically in the section at C of FIG. 4, the metal workpiece has been cold reduced to the desired thickness and the surface thereof has been suitably cleaned without resort to acid pickling operations of any nature whatsoever. Test data indicate that cold worked metal workpieces processed according to this invention evidence a contaminant-free surface comparable to the surface of blast cleaned hot rolled workpieces before cold working.

Thus, a method and apparatus to cold work and surface-clean metal workpieces has been disclosed which removes surface as well as sub-surface contaminant without resort to cumbersome and expensive acid pickling processes The disclosed invention makes use of abrasive and/ or ultra-sonic cleaning equipment which is readily available and occupies materially less plant floor space than large acid pickling tanks. Additionally, the cleaning process of this invention overcomes the problems encountered in previous attempts to clean contaminant from metal workpieces by means of blast cleaning without acid pickling prior to cold reduction. The additional provision of a final ultra-sonic or blast cleaning step cooperates with the rest of the assembled apparatus to achieve a surface preparation combination providing materially improved results. It should be emphasized that the second cleaning step also removes any contaminant also deposited on the metal workpiece by thereducing rolls as mentioned in the earlier portion of the above description.

While the above described embodiments constitute preferred modes of practicing this invention, other embodiments and equivalents may be resorted to within the scope of the actual invention, which is claimed as follows.

What is claimed is:

1. An assembly for providing surface-clean cold rolled sheet metal workpieces comprising abrasive blasting means for first removing exposed surface contaminant from said sheet metal workpieces, cold rolling means for reducing the thickness of said surface cleaned sheet metal workpieces and which mechanically-upsets the surface layers of said sheet metal workpieces during said rolling to alter the grain structure thereof exposing sub-surface contaminant, ultrasonic cleaning means for removing said exposed sub-surface contaminant from the work-pieces, and means for moving said workpieces through each of said above means in the order presented.

2. An assembly for providing surface-clean cold rolled sheet metal workpieces comprising abrasive blasting means for first removing exposed surface contaminant from said sheet metal workpieces, cold rolling means for reducing the thickness of said surface cleaned sheet metal workpieces and which mechanically upsets the surface layers of said sheet metal workpieces during said rolling to alter the grain structure thereof exposing sub-surface contaminant, abrasive blasting means for removing said exposed sub-surface contaminant from the workpieces, and means for moving said workpieces through each of said above means in the order presented.

3. A method for producing surface-clean cold rolled metal workpieces comprising the steps of first blasting the said sheet metal workpiece surfaces with abrasive to remove surface contaminant therefrom, cold rolling said surface cleaned sheet metal workpieces to reduce the thickness thereof and which mechanically upsets the surface layers of said workpieces to alter the grain structure thereof exposing sub-surface contaminant, and finally blasting the cold rolled workpiece surfaces with abrasive to remove said exposed sub-surface contaminant and any additional material deposited on said workpiece surfaces by the cold rolling steps.

4. A method for producing surface-clean cold rolled sheet metal workpieces comprising the steps of first blasting the said sheet metal workpiece surfaces with abrasive to remove surface contaminant therefrom, cold rolling said surface cleaned sheet metal workpieces to reduce the thickness thereof and which mechanically upsets the surface layers of said workpieces to alter the grain structure thereof exposing sub-surface contaminant, and finally ultrasonically cleaning the cold rolled workpiece surfaces to remove said exposed sub-surface contaminant and any additional material deposited on said workpiece surfaces by the cold rolling step.

References Cited by the Examiner UNITED STATES PATENTS 2,239,580 4/1941 Staz 51-,5 2,554,701 5/1951 Hackett et al. 51-281 2,867,949 1/ 1959 Meyer 51-5 2,877,534 3/1959 Larsen et al. 2981 2,907,151 10/ 195 9 Peterson 51324 2,913,808 11/1959 Thomas et al 29-81 2,966,425 12/1960 Fucinari et al. 60.6 X 3,031,802 5/ 1962 Leliaert 519 3,188,776 6/1965 Dill 51-14 X ROBERT C. RIORDON, Primary Examiner.

LESTER M. SWINGLE, Examiner.

I. A. MATHEWS, Assistant Examiner. 

1. AN ASSEMBLY FOR PROVIDING SURFACE-CLEAN COLD ROLLED SHEET METAL WORKPIECES COMPRISING ABRASIVE BLASTING MEANS FOR FIRST REMOVING EXPOSED SURFACE CONTAMINANT FROM SAID SHEET METAL WORKPIECES, COLD ROLLING MEANS FOR REDUCING THE THICKNESS OF SAID SURFACE CLEANED SHEET METAL WORKPIECES AND WHICH MECHANICALLY UPSETS THE SURFACE LAYERS OF SAID SHEET METAL WORKPIECES DURING SAID ROLLING TO ALTER THE GRAIN STRUCTURE THEREOF EXPOSING SUB-SURFACE CONTAMINANT, ULTRASONIC CLEANING MEANS FOR REMOVING SAID EXPOSED SUB-SURFACE CONTAMINANT FROM THE WORKPIECES, AND MEANS FOR MOVING SAID WORKPIECES THROUGH EACH OF SAID ABOVE MEANS IN THE ORDER PRESENTED. 